1. Technical Field
Embodiments of the present invention generally relate to a developer amount detector, a developing device, a process unit, and an image forming apparatus, such as a copier, a printer, a facsimile machine, or a multifunction peripheral (i.e., a multifunction machine) including at least two of these functions.
2. Description of the Related Art
Electrophotographic image forming apparatuses, such as copiers, printers, facsimile machines, and multifunction peripherals (MFPs) having at least two of copying, printing, facsimile transmission, plotting, and scanning capabilities, include a developing device to develop latent images on a latent image bearer such as a photosensitive drum or a photoconductor drum. Typically, developing devices include a toner containing compartment to contain toner and a developing roller to supply toner contained in the toner containing compartment to the photosensitive drum. As the developing roller supplies toner from the toner containing compartment to the photosensitive drum, an electrostatic latent image on the photosensitive drum is developed.
To reduce the size and cost of developing devices, toner may be contained not only inside the developing device but also in a cartridge (i.e., a toner container) from which toner is supplied to the developing device. This configuration is becoming a mainstream at present. In this case, the amount of toner in the developing device is detected, and the developing device is replenished with toner supplied from the cartridge as the amount therein decreases. At that time, if the amount of toner supplied from the cartridge to the developing device is extremely large, there is a risk that powder pressure inside the device rises to cause toner to scatter out from a supply inlet. By contrast, if the amount of toner supplied from the cartridge to the developing device is extremely small, there is a risk that the amount of toner supplied to the developing roller, and further to the photosensitive drum, becomes insufficient. In either case, image quality degradation or leak of toner can arise, and thus the quality of printing is affected adversely. Accordingly, to secure the image quality, it is preferred to accurately detect the amount of toner inside the developing device and supply toner from the cartridge to the developing device reliably and quantitatively. Detecting the amount of toner remaining accurately and supplying toner to the developing device at proper timing are desirable particularly in compact developing devices since an inner volume of the toner containing compartment is smaller in the compact developing device.